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What should you watch out for when creating or moving F runtime groups and using the F library "Failsafe Blocks (V1_2)" or "Failsafe Blocks (V1_1)"?

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Description:To optimize reaction times for the F program, certain blocks of the S7 F system are automatically moved into the first or last runtime group of their disabling group during compilation. If an F runtime group is placed before the first or after the last F runtime group, this might result in passivation of F I/Os or of the CPU-CPU communication during the delta load.

When should you expect this behavior?
You should expect the behavior described above in the following cases:

If you divide or regroup disabling groups by placing/deleting the F_PSG_M block.

If you move F runtime groups manually in front of the first or after the last F runtime group of an F disabling group.

When copying or recreating F charts in the CFC or SIMATIC Manager because this automatically generates F runtime groups.

How can you prevent this behavior?
You can never avoid this behavior if you redistribute runtime groups by placing/deleting/moving the F_PSG_M block. In this case, the module drivers and communication blocks must be moved from one disabling group to another. (See note in the manual "Configuring and programming S7 F/FH systems" on page 140).

Otherwise you can avoid passivation by using the F library "S7 F System Lib V1_3". If you use F library "Failsafe Blocks (V1_2)" or "Failsafe Blocks (V1_1)", you can avoid the behavior as follows:

Time

Action

Before inserting F charts

Before copying or recreating F charts, ensure that the global installation pointer of the CFC is pointing between the first and last F runtime group of an F disabling group. You recognize which runtime group the installation pointer is pointing at by the green background of its name in the runtime order. If necessary, set the installation pointer by selecting the desired F runtime group by right-clicking the mouse and choosing the option "Predecessor for Installation".

If you are directly editing or creating F runtime groups, ensure that these are always between the first and the last F runtime group of an F disabling group.

Before delta loading

Before delta loading, check by way of example for one input and output module driver per disabling group, to ensure that these module drivers were not deleted in a runtime group. Use the dialog "Compare security programs" of S7 F systems and compare the security system to be loaded with the most recently loaded status. (This must have been saved after the last loading process, as a reference, for example).

If the input module driver of a disabling group was deleted in a runtime group, then move this F runtime group to the first position of the disabling group.

If the output module driver of a disabling group was deleted in a runtime group, then move this F runtime group to the last position of the disabling group.

Note: You can avoid checking the output module driver if you use S7 F systems as of V5.2 SP4.